1. Field of the Invention
The present invention relates to a process for the solubilizing of a high melting polymer so that the solubilized polymer can be formed into a desirable shape. More specifically, the present invention relates to the solution at temperatures of between about 240.degree. to 400.degree. C. of poly(etheretherketone) type polymers using organic compounds generally having a high boiling point, forming the solubilized polymer into a shape, removing the organic compound(s) and recovering the shaped article.
2. Description of Related Art
Poly(etheretherketone) is a very useful recently developed high temperature polymeric material. The properties of commercially available PEEK include:
1. A relatively high glass transition temperature of about 144.degree. C., PA1 2. A very high crystallized melting point of about 341.degree. C., PA1 3. Thermal stability, and PA1 4. High solvent resistance.
Unfortunately, these properties make PEEK a very difficult polymer to mold into desirable useful shaped articles. Specifically, the thermal stability and solvent resistance make PEEK an ideal candidate for ultrafiltration and microfiltration membranes, hollow fibers, said fibers and the like. However, the very useful thermal and solvent resistance of PEEK often presents severe problems in shaping the polymer into a desired useful form.
Formation of articles of manufacture from PEEK requires special solvents for the polymers. Generally, PEEK is advertised as being insoluble in all common solvents and, being crystalline, has excellent resistance to a very wide range of organic and inorganic liquids.
Most of the art describes simple relatively low boiling solvents used to dissolve the monomers to prepare the PEEK. Once PEEK is formed, it usually separates from the polymerization solvent(s).
The art includes for example:
H. A. Smith in U.S. Pat. No. 4,118,363 discloses that diphenyl ether is used as a high boiling solvent for high molecular weight solvent resistant crystalline polymers, such as poly(phenylene sulfide). Further, the alkyl-substituted and halogen-substituted diphenyl ethers are useful high boiling solvents for poly(phenylene sulfide). Diphenyl sulfone (molecular weight 218, melting point 124.degree. C., boiling point 379.degree. C.), dissolves about 70% of PEEK polymer at 380.degree.-390.degree. C. (in excess of the boiling point).
1-Chloronaphthalene (molecular weight 162, melting point -20.degree. C., boiling point 258.degree. C.) and benzophenone (molecular weight 182, melting point 50.degree. C., boiling point 305.degree. C.) are suggested as solvents. However, the useful solvent abilities are somewhat restricted by their relatively low boiling points.
Concentrated sulfuric acid, chlorosulfonic acid or trifluoromethanesulfonic acid are other "good" solvents for PEEK. However, the treatment of PEEK with these strong acids, usually at elevated temperatures, may result in a "new" sulfonated polymer, which is soluble in the solvent acid, and is completely different from the original polymeric PEEK.
It is not possible a priori to determine those organic compounds which will be useful as solvents to produce useful articles comprising PEEK. It is therefor extremely useful to have performed a large number of experiments to determine those solvents which are useful to dissolve (or to solubilize) PEEK.
None of the above references individually or in combination teach or suggest the use of a number of high boiling solvents comprising organic compounds to solubilize poly(etheretherketone), forming the solubilized poly(etheretherketone) into the shape of an article of manufacture, removing the solvent and recovering the article of poly(etheretherketone).